The invention described herein related to the packaging of electronic processing components in a computer system, and more particularly to an apparatus which provides for the monitoring and modification of electrical connections between the electronic processing components.
As airplane and spacecraft have become more technologically sophisticated, there has been a greater need to include more electronic components on the vehicles. For example, avionics systems which are employed to control flight and other aspects of the aircraft and/or spacecraft, require a great number of electronic processing components as well as input/output and interconnected signal lines so that the various components may communicate.
Typically, an aircraft or spacecraft will carry a number of xe2x80x9cblack boxesxe2x80x9d which include circuit cards designed to perform particular functions. A number of circuit cards may be positioned in each black box and electrical connections provided from each circuit card. These electrical connections may be made to a motherboard, which in turn provides for communication from a particular black box with any number of remotely located systems.
The integrated circuits which are employed in the black boxes described above may be packaged in what is known as a multichip module (MCM). A MCM is a chip carrier within which various computer chips may be located with electrical connections provided between chips as well as to external components. Most commonly, these multichip modules are incorporated in multi-layer dielectric substrates that employ thin film processes for form electrically conductive traces to interconnect the various chips. The multi-layer dielectric substrates are made employing techniques that have been initially developed for various types of semi-conductive type processing. These MCMs may include high density interconnect (HDI) technology. In an MCM, many chips may be connected in close proximity to each other.
When MCM""s or other electronic components are included in an electronic assembly, a typical configuration is incorporate external electrical contacts on the outside surfaces of these components and to stack these items in a manner such that desired electrical connections are established. Once the components are aligned, a compressive force may be applied to hold the assembly together. One draw-back of this configuration is that over time the physical characteristics of the external electrical contacts may deteriorate such that electrical resistance across the contacts may vary. The inventor has recognized that certain apparatus may be provided with the electronic assembly and certain steps performed during operation of the electrical components such that good electrical connections may be maintained.
Described herein is an electronics apparatus which includes the functionality for measuring the quality of certain electrical contacts within a stacked electronic assembly and for performing certain steps to improve the conductivity through these contacts when detected resistance rises above a pre-determined level. Included in the apparatus are a plurality of electronic components wherein each of these components has at least one external electrical contact. Running through each of the electronic components are conductive traces which comprise a feedback circuit over which pre-determined current may be transmitted such that a voltage drop over the circuit may be measured. This measurement may be converted to a resistance calculation for the circuit.
Further included in the electronics apparatus may be a force actuator device which is in electrical connection with the resistance measurement device. The force actuator device may include at least one force actuator which is positionable on the electronic assembly such that it may exert a compressive force on the stacked electrical components when activated. This activation may be in response to receipt of a control signal from the resistance measurement device.
In one configuration of the invention, the electronic assembly components may include a multichip module (MCM), an interposer, and a circuit card interface for providing interconnection of the electronic assembly with remotely located systems. These electronic components may be in a stacked configuration such that the external electrical contacts on the external surfaces of each of the components are in contact with each other. In the stacked configuration, the interposer is positioned between the MCM and the circuit card interface. The interposer is configured such that the electrical contacts run through the thickness of this component. The contacts may be shaped such that when a compressive force is applied to said contacts, the external portions of the contact move in a desired fashion. In one configuration of the invention, these components may have a xe2x80x9cZxe2x80x9d shape.
To provide for the application of a compressive force to the electronic assembly described herein, a base plate structure may be provided wherein this structure includes a plurality of alignment pins extending therefrom. Incorporated into the other components of the assembly described herein, may be alignment holes through which said pins may pass. When the components are in the stacked configuration and the alignment pins are running through each component, the external electrical contacts on each of the components shall be in electrical connection with their electrical contacts.
On the opposite side of the stacked configuration from the base plate structure may be the resistance measurement device and force actuator assembly in a self-contained structure. This structure may be configured such that it includes apparatus for receiving and engaging the alignment pins. The alignment pins may be received by specially configured force actuation motors which contact the alignment pins and apply a force to said alignment pins such that a desired compressive force is applied to the stacked electronic assembly. In one configuration of the invention, the force actuator devices may comprise piezoceramic inchworm motors which attempt to move along the alignment pins in response to a received voltage. In another configuration of the invention, the force actuators may comprise at least one shape memory alloy motors positioned relative to the stacked electronic assembly which is in electrical connection with a controller such that the motors moves in a fashion such that a variable compressive force is applied to the stacked electronic assembly. In yet another configuration of the invention, electromechanical actuators may be physically attached to the exterior surfaces of the electronic assembly where an electrical connection is established between the actuators and an electronic controller.
In yet another configuration of the invention, the current source, voltage measuring device, and force actuator may be incorporated into a microprocessor. This microprocessor may include external pins or connectors for establishing a connection with the feedback circuits as well as the force actuators which are employed.
The stacked electronic assembly described herein may be further be employed in a specially adapted system for loading and unloading MCMs. Included in this apparatus is a black box structure for holding a plurality of stacked electronic assemblies. Electrical connections are provided through the black box structure such that electrical signals may be transmitted via the circuit card interface to remotely located structures. In connection with the black box structure is a movable MCM magazine which is electrically controllable to move in a desired direction relative to position of electronic assemblies within the MCM stack structure. Further, an MCM insert/remove actuator is employed in conjunction with the MCM magazine such that one MCM can be removed from the stacked electronic assembly and a new one inserted. The MCM stacked structure can be configured such that electronic signals may be transmitted to the force actuator such that the alignment pins may be released and the base plate structure and alignment pins removed from the stacked assembly. The MCM which is to be replaced may then be removed and a new one replaced through the use of the insert/remove actuators.
In operation, the electronic assembly described herein may be first assembled by positioning the electronic devices such that the external electrical contacts are in contact with electrical contacts of the other electronic components. This may be done by having the alignment pins of the base plate structure pass through the alignment holes of each of the electronic components. Once this device is assembled and in operation mode, a current of a pre-determined magnitude may be periodically transmitted through the above-described feedback circuit. A voltage measurement device employed in conjunction with the current source may then measure the voltage drop over the feedback circuit. If the measured voltage drop is greater than a pre-determined value, this would indicate that the resistance across the electrical contacts is greater than desired. In response to detection of the high resistance, a control signal may in turn be transmitted to the force actuators which are employable for exerting a compressive force on the stacked components of the electronic assembly. As the compressive force is applied, additional measurements may be made across the feedback circuit to provide additional measurements of the resistance. Once the resistance is less than a pre-determined value, the change in compressive force may be stopped.
The system described herein may be programmed such that the current transmission and voltage measurement may be performed at pre-determined intervals. Further, the system may also be configured such that the current transmission is controlled manually and may be initiated by a user interface remotely located from the electronic assembly but in electrical connection.
The system may be further configured such that a compressive force is applied to the stacked electronic assembly through the force actuators. This force provides for moving the electrical contacts in the interposer in a lateral direction such that a scrubbing action occurs between said contacts and the electrical contacts on other electronic components. This scrubbing action acts to remove any substances which are increasing the resistance across the contacts.